Traffic control system and apparatus



May 6, 1941. H. A. wxLcox TRAFFIC CONTROL SYSTEM AND APPARATUS Filed Feb. 2o. 195s 6 Sheets-Sheet 1 HDN uhh

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INVENTOR AH/mvx/ ,4. M//ax mm/MQ, @mju 1PM A TT ORNE YJ May 6, 1941. H. A. wlLcox 2,241,047

TRAFFIC CONTROL SYSTEM AND PPARATUS Filed Feb. 20, 1936 6 Sheets-Sheet 2 A TT ORNE YJ May 6, 1941. H. A. wlLcox TRAFFIC CONTROL SYSTEM AND APPARATUS Filed Feb. 20, 1936 `6 Sheets-Sheet 4 V- --f /NVENTOR I BY Hafer A. W/cax May 6, 1941. H. A. wlLcox' TRAFFIC CONTROL SYSTEM AND APPARATUS Filed Feb. 20, 1936 6 Sheets-Sheet 5 Y M45 m2 y J B uff v May 6, 1941- H. A. wlLcox 2,241,047

TRAFFIC CONTROL SYSTEM AND APPARATUS `Filed Feb. 2o., 193e e sheets-sheet e M4575@ Co/v maui@ l 9 l no2/awww@ Pas/naw /N VEN 7` 0R HAeey A W/z cox .4 TTORNE YS Patented May 6, 1941 Harry A. Wilcox, Bronxvllle. N. Y., assignor to Automatic Signal Corporation, New York, N. Y., a corporation of Delaware Application February zo. 193e, serial No. 64,341

This invention relates to traiiic control systems for interfering tramo lanes, particularly to those systems of the traillc actuated type in which vehicles, pedestrians, or other trai'iic elcments indicate their presence to a traillc signal controller through traiiic detectors and influence the timing of traiilc signals, and is especially concerned with means for supervising the operation of individual systems of that type at different intersections so as to provide for coordinated movement of traillc passing successively through the several different intersections.

Systems are well known in the prior art for supervision of individual local trailic signal controllers of these-called ilxed time or non-trame actuated type by some form of master controller to resynchronize the local controllers periodically so as to maintain a predetermined simultaneous or sequential progressive relation between the times of transfer of. right of way between the intersecting streets at the different intersections, and thus provide for coordinated movement of traffic through the several intersections.

Trailic actuated control systems for the control of individual or isolated street intersections have also been in use for several years and more recently arrangements have been employed to supervise the transfer of right ofway from a main highway to a cross road by a trailic actuated signal controller in response to actuation of such controller by trailic on the cross road to coordinate such transfer with any corresponding transfers occurring at other intersections. Such supervision has been usually in the form of a common master timer with connecting circuits' to several individual local intersection trame signal controllers for Irestricting the transfer of right of way from the main highway at one or more of such individual intersections in response to trai'ilc actuation on the respective cross roads at the latter. In such systems the right of way normally remains continuously on the main highway in the absence of cross road actuation. The master timer cyclically opens and closes such circuits for example for predetermined periods to control when the local controllers can and cannot respond to traiiic actuation and thus coordinates the actions of the different local timers for th benefit of through highway tramc.

The master timer has in some cases been a single centralized control and in other cases has been in the form of individual synchronous motor driven master timers associated with the individual local signal controllers, the synchronous the local controller can transfer right of way to vso its cross road if trafc actuation at its cross road has occurred. In a total background cycle of 60 seconds for example this permissive period might range in length from 5 to 30 seconds, the length selected for a vparticular intersection depending on the traflic conditions there and its relation to the coordination plan for all intersections.

'Ihe preventive period is generally the compleinent of the permissive period, as when the permissive period for cross road traiiic is 10 seconds out of a 60 second background cycle for example, the preventive period would ordinarily be the remainder of the cycle or 50 seconds.

\The permissive" and preventive periods may either be arranged to cause all local controllers that have been actuated by traffic to transfer right of way substantially simultaneously, or they may be arranged to cause right of way to be transferred at the several intersections in progressive sequence to provide progressive trame movement down the highway.

It has been found with these prior systems of supervisory control, where the point of control of the master timer over the local timer is at that point in the local timers signal cycle where right of way is transferred to the cross road, that the permissive period during which the local timer can respond to cross road traillc actuation and transfer right of way to the cross road must be quite short, since the longer this period is made the more chance there is for the local timer to transfer right of way to the cross road later than the best time for coordinated movement, and if the period of right of way accorded to the cross road is required by cross trafc to be fairly long, the amount of delay in transferring right of way to the cross road will also be reflected in returning right of way to the main highway. 'I'he right of way return to the main highway may thus be carried over into that portion of the background cycle assigned for main motors maintaining the individual master timers highway right of way and traillc arriving at the 2 y intersection on the main highway in progressive movement thereby interfered with and delayed.

This new system overcomes these dimculties and provides in accordance with the invention an arrangement for causing the return of right of background cycle assigned to the cross road the return of right of way to the main highway at the proper point in thebackground cycle will be assured by supervisory action of the master timer on the local timer. Thus in accordance with the invention the permissive period for transfertof right of way to the cross road may be made t extend through a large part of the cross road right of way portion of. the background cyclei and thus cross road trafiic actuating the local controller is given a longer opportunity to initiate right of way transfer for its benefit.

'I'he earlier trail'ic actuated control systems subject to supervisory coordination control of the permissive type mentioned were in some cases provided with means in the local control- 1ers for varying the cross road right of way pebeing provided in cooperative relation so as to restrict the transfer of right of way only so, far as required in each cycle to enable the local controller to be in condition at these appropriate riod between a minimum and a maximum depending on the demand of cross road traflic as shown by trafc actuation, during the cross road period. This flexibility of the local controller however offeredV a problem in coordinated control systems because it increased the possibility of right of way being held on the cross road over into the main highway portion of the background cycle. This difficulty is also overcome by the invention in assuring that variation of the cross read right of way period cannot carry beyond the end of the cross road right of way portion of the background cycle.

Another limitation in past systems has been that'supervisory control only of the transfer of points in the background cycle to transfer right of way to the proper streets if such transfer should be required by traffic actuation, and to allow the local controller to transfer right of way and maintain right of way throughout the remainder of the background cycle in accordance with the demand of traffic as shown by tramo actuation. Thus the invention provides as will be later described in detail that a number of individual flexible traffic actuated controllers of either the full actuated or semi-actuated type or both may be coordinated in a manner to assure that in the' presence of trafiic the right of way will be accorded to the proper street at the proper time in accordance with the predetermined coordinated plan of the background cycle, but that as traiiic varies from the pattern of the background cycle the local controller will be permitted to vary the proportions of time right of way is accorded to the intersecting streets.

It is an object of this invention to provide an improved system for coordinating the operation of a plurality of individual traffic actuated tramo signal controllers at a number of intersections of interfering traffic lanes to promote the smoother movement of traflc successively thru the several intersections.

Itis another object of the invention to coordinate the operation of individual traffic acturight of way from the main road to the cross road offers no effective way of co-ordinating two local controllers where one or both were of the full actuated type.

It will be appreciated at this point that the so-called main and cross roads may have substantially equal traffic, or the traiiic on the cross road might at times exceed that on the main road. The terms main road or highway and cross road are therefore to be construed generally with full actuated control and not necessarily to infer always that the main highway has more traillc than the cross road.

The terms semi-traffic actuated and semiactuated control systems are used herein to designate a tramo control system for an intersection in which traiiic actuatable devices are located only in the cross road, the right of way being normally accorded to the main road in the absence of actuation on the cross road, and being transferred to the cross road in response to cross road tramo actuation, and after a period which may vary between a minimum and a maximum in accordance with traffic actuation, being retransferred automatically to the main road.

The new system arranged in accordance with the invention provides means of controlling from the master controller both the transfer of right of way from each street and the return transfer of right of Way to each street by the local controller at appropriate points of the background cycle of the master controller, these functions ated controllers at different intersections so as to favor the movement of traic thru the several intersections in accordance with a predetermined coordinated plan, but also to provide a high degree of flexibility for the individual controllers to depart from that plan insofar as traffic at such individual intersections differs from that on which the plan was based.

Y It is an additional object of the invention to supervise cyclically the accord of right of way by a traflic actuated signal controller at an intersection so as to favor the accord of right of way to one street at the intersection during one portion of a time cycle when traffic is present on that street during that portion of such cycle.

It is a further object of the invention to supervise cyclically the accord of right of way by a traffic actuated signal controller at an intersection so as to favor the accord of right of way to one street at the intersection during one portion of a time cycle and to favor accord of right of way to an intersecting street during another portion of the time cycle when trafc is present on the particular street in its respective portion of the time cycle.

It is another object of the invention to supervise a. trailc actuated signal controller at an intersection in accordance with a master control cycle such that during a portion oi such cycle the arrival of traffic on a preferred street at the intersection while right of way is being accorded to another street will cause substantially immediate transfer of right of way to the preferred street.y

It is also an object of Ithe invention to supervise a tramo actuated controller at an intersection so that cyclically for predetermined periods the transfer of right of way from a preferred lane to an intersecting lane is prevented if it has not previously occurred, and during the latter portion of Said period the transfer of right oflway to such preferred lane from such intersecting lane is required in the presence of traiiic on such preferred lane if right of 4way has been on such intersecting lane regardless of trame actuation demand on such intersecting lane.

It is a further object of the invention to supervise a traiiic actuated controller as described in lche last mentioned object but providing such cyclic predetermined periods successively for the dierent lanes so that during a part of the cycle one lane is made the preferred lane and during another part of the cycle an intersecting lane is made the preferred lane.

It is another object of the invention to provide a tramo control system in which individual signal timers at different intersections along a preferred street are arranged to be fully actuated by vehicles on the preferred street and on a cross street lbut in which a progressive movement of traffic along the preferred street will be favored by assuring that at and immediately prior to thetime when a group of vehicles in the progressive movement on the preferred street are scheduled to arriverat each intersection if the individual timer at that intersection is according right of way to :the preferred street the transfer of right of way from the preferred street will be prevented, and if the individual timer is according right of way to a cross street the transfer of right of way to the preferred street will be assured in time to avoid stopping any vehicles to arrive in such group.

It is a further object of the invention to provide a trame control system in which tramo signal timers at individual intersections along a main street normally accord right of Way to the main street but upon actuation by tranic on a cross street transfer right of way to such cross street for a period which may be dependent upon the amount of tramo actuation on that cross street and thereafter retransfer right of way to the main street, and in which coordinated movement of traili-c along the main street is provided for by providing a cycle of supervisory control over the individual timers in a predetermined portion of which right of way is assured to the main street, the transfer of right of way to the cross street being permitted only during a certain portion of the cycle, and the retransfer to the main street xbeing assured before the .beginning of the main street predetermined assured portion of the cycle.

Prompt transfer of right of way Ito a preferred traiiic lane in case right of way g on an intersecting trailic lane.

Other objects will subsequently appear and considering now one form of' apparatus embodying the invention, referrence may be had to the following figures in which:

lIiligure 1 illustrates a series of intersections along a street on which coordinated trame movement is desired, the several intersections being equipped with different types of trafiic control apparatus interconnected .to be supervised in accordance with the invention.

Figure 2 illustrates how apparatus may be placed in accordance with the invention to provide coordinated tramo actuated control throughout a grid of intersections, providing for coordinated movement of tramc through both northsouth and east-west series of intersections for example.

Figure 3 shows a schematic diagram of a time cycle of supervisory control for a fully tramo actuated trafiic signal control system at a typical intersection in accordance with the invention.

Figure 4 4shows a time cycle of supervisory control for a semi-trame actuated signal control system at a typical intersection.

Figure 5 is a schematic circuit diagram of an illustrative form of a full tralc actuated. traiiic control system at a typical intersection and its supervisory control embodying the invention.

Figure 6 is a schematic circuit diagram of one form of semi-tralc actuated control system at another intersection and its supervisory control embodying .the invention.

Figure 7 shows an alternative form of supervisory control of a full traiilc actuated system.

It is another object of the invention to provide I a Itraffic actuated signal control apparatus for an individual intersection which is adapted to fit into fixed time or non-traffic actuated progressive systems along a preferred street passing thru this trol system which accords right of lway alternately to intersecting traiiic lanes between minimum and maximum time limitsin accordance with trafilc actuation on such lanes, a mech-anism for connecting such systems to a fixed time or other cyclic supervisory system so that during a certain portion of the supervisory cycle the maximum time limit is shortened to force the The signicance and operation of the new system of this invention may perhaps best -be understood by visualizing it as comprising individual traffic actuated signal control systems at each of a number of intersections with a so-called fixed time or non-actuated progressive system superimposed, the trafilc actuated systems having the direct control of the signals, and the progrelve system providing cyclic control in the background over the tramo actuated systems so as to favor the accord of right of way for example first to the main street in one part of the progressive system cycle and then tothe cross street in another part of this background cyclein eiect cyclically making rst one street and then the other a preferred street, in predetermined simultaneous or sequential time phase at the several intersections.

This supervisory effect of the progressive system background cycle can be made operative on the trafiic actuated controller so that during substantially the entire portion of the 'background cycle during which right of way would ordinarily be accorded to one street .by the progressive system :the transfer of right of way from that one street to the other street in response to actuation on the latter is prevented, and correspondingly during the portion of the background cycle assigned fcr right of way to such other street the transfer of right of way to the one street is prevented. This eil'ect can be supplemented by having the progressive system force immediate transfer of right of way to the preferred street in its portion of the background cycle in response to any traiilc actuation on that street. The combination of these -two effects is to cause the right of way to be accorded to the respective streets by the tram-c actuated controller in accordance way to the preferred street at the beginning of its period in the .presence of traffic, the tramo actuated controller then being released from the supervisory control effects for substantially the balance of the period for the preferred street, the right of way being controlled after such release solely by tramo demand, traillc actuation on the preferred street holding the ri ht of way and trailic actuation on the intersec ing street causing transfer of right of way from the preferred street as soon as tramo ceases for an appreciable period on the latter street. It Will be understood the intersecting streets will be alternately treated as the -preferred street for predetermined portions of the background cycle.

The'use of the apparatus of the invention will de described and shown applied both to full and to semi-traffic actuated traffic signal controllers, and also to non-tramc actuated controllers.

. Referring now to Figure .l there is represented a series of intersections of a common street A with cross streets, each of the intersections i shown being provided with a, tramo signal, and controller therefor which may for instance be of the types designated in the figure. Trafc actuatable detectors are lplaced in the intersection approaches where desired and connected to `the proper signal controller. A master controller is also shown, comprised of a series of contact discs or other suitable contact devices continuously driven in synchronism by a motor M which is preferably of 'a constant speed type. By means of the contact discs, supervisory control circuits to the controllers at the several intersections shown are completed and interrupted in certain parts of the cycle of the contact discs in a predetermined arrangement. Similarly the control circuits to controllers at other street intersections may be made and 'broken by properly designing the contact disc segments. It will be understood that all the intersections might be equipped with full actuated controllers or semiactuated, or any combination required for adequately serving the series of intersections in question. It will also be obvious to those skilled in the art that pedestrian push buttons or switches could be connected to the controllers for actuation by pedestrians to supplement or take the place of vehicle actuation, and trolley contactors or other well-known forms of street car or railway actuating devices might be employed for such trafiic as well as automotive or other road traflc. The term traffic is therefore to be considered as broadly including all such trame elements. y

Figure 2 represents the installation o'f a system of this general character to a grid or checkerboard of intersecting streets showing a number of full trailc actuated, semi-actuated and nontrailic actuated signal controllers and their connections to a master controller for supervising the cycles of all the individual intersection controllers. The control circuits from the master to the supervisory control relays at each controller may be arranged to be energized at the proper times to permit progressive movement of tramo in both directions on each of the streets in the group. Further explanation of such signal operation as well as the method of accomplishing will be described below.

Referring now to Figs. 3 and 4'the schematic cycle diagrams for the background supervisory control time cycle as applied to two types of local signal controllers show the interrelation/of the several portions of the supervisory cycle and their significance in. connection with the preferred right of way signal periods of the background cycle (right of way being indicated in the figure as R. O. W. to conserve space).

Figure 3 shows one preferred form of supervisory cycle to be applied to a full-traffic actuated local controller as illustrated at the interl section of A and B streets for example in Fig. 1- and Fig. 5. Beginning at the top at the point O the time cycle can be traced clockwise around the circle passing the point marked T and returning to O and repeat. The radial lines at point O and T show the division of the background cycle into a .portion O-T assigned for right of way to A street and a following portion T-O assigned for right of way to B street. It will be understood that this is not the actual division of rightvof way signal display periods at the full traine actuated control intersection lbut only the preferred division for best coordination with other intersections in the progressive system or other suitable complete control system for the entire group of intersections. In the case of a xed time or non-actuated controller as for example at intersection Z however the division of right of way periods shown on the outer circle of the diagram is also the actual division of right of Way by the signals. In the case of full traffic actuated control the actual signal displays do not normally correspond exactly with the division of the background cycle as shown on the diagram, but vary more or less from this division depending upon whether tramo is light or heavy respectively at the intersection. If traillc is very light for example and there is trailic on B street but no tran'ic on A street during the A street portion of the background cycle the right of way may remain on B street during a large part or all of the A street portion of the cycle. With substantially continuous traflic approaching on each street the actual signal display would correspond with the background cycle division and phase relations shown.

The supervisory control thus primarily favors the transfer of right of way to'and the holding of right of way on nrst one street and then the other byy the local trailc actuated controller. These eiects can be seen by further reference to Fig. 3, considering for example the point T at which transfer of right of way from A street to B street is to be favored by the supervisory control. It will be noted that prior to the point or line T there is a period extending from the point or line BP to T designated as the B street preparatory period. During this period no transfer of right of Way from B street is permitted (if right of way is already on B street), but transfer of right of way to B street (if right of way is on A street) is not yet forced. Thus if right of way is on A street during this period it may be held there by actuations -of traffic on A street but if right of Way is on B street it cannot be transferred to A street during this period.

Ordinarily the time interval of this preparatory period is set to correspond with the minimum time required in accordance with the normal` time intervals of the individual local 'controller to 'transfer vright of way to A street and back to B street. For example if the yellow interval after vB street right of way is 3 seconds, the A street initial green interval is 5 seconds, the A street vehicle interval given is 5 seconds and the yellow interval after A street right of way is 3 seconds the sum of these intervals or 16 seconds is the shortest normal .time in which.

rightof way can be transferred from B street and be returned to it, and the B street preparatory period is correspondingly' set at 16 seconds. The preparatory period mayoi' course be set trated.

longer than the sum of these several intervals as described but it is preferably not set any shorter, so as to avoid the possibility of transfer of right of way from B street so late in the 1?` After passing thepoint T in the supervisory cycle in Fig. 3 it will be seen that a right of way guarantee period" for B street is provided, extending to the line BG. 'I'his is the portion of the cycle in which right of way is assured to B street if any traffic is present on B street as shown by actuation of the B street detectors. It can also be arranged to have automatic transferof right of way to B street at the beginning of this period even without B street tramo actuation if desired as will be more fully explained subsequently herein. v

Preferably however the supervisory control is arranged so that if right of way is on A street at the beginning of this B street rightof way guarantee period and no traffic actuation has yet occurred on B street the right of way will continue on A street to care for any further trame on A street. As soon as the first vehicle arrives on B street during this guarantee period however transfer of right of way to B street is caused immediately by the supervisory control in spite of any traillc on A street. Correspondingly if a vehicle-is waiting on B street while right of way is held by traffic on A street at point T immediate transfer of righi'l of way to B street is caused through the supervisory control. `In each case such transfer preferably includes the usual yellow clearance period.

During the B street right of way guarantee period the transfer of right of way to A street is still preferably prevented by the supervisory control so that when right of way is on B street during this period it will be held tothe point BG to care for the arrival of a group of vehicles which may be lagging behind the front of a progressive wave for example. Also in cases where a progressive wave of vehicles eastbound for example is scheduled to arrive some time after the westbound wave, this serves to hold the right of way on B street until the time when the eastbound wave is scheduled to arrive.

'I'hus it will be seen that two functions are performed by the supervisory control in connection with the preferred right of way transfer point T. First, during the entire period from BP to BG (i. e. the sum of B street preparatory period and B street right of way guarantee period) transfer of right of way from B street is prevented if right of way is on B street; and second. from T to BG (i. e. the B street right of way guarantee period) the transfer of right of way 'to B street is forced immediately upon B street Continuing around the cycle diagram in a clockwise direction the period from BG to C is designated as the B -street traillc actuated right of way extension period during which tramo on B street may continue to hold the right of way. During the first part of this period, i. e. from BG to AP. the tramcactuated controller is free of any restrictions by the supervisory control Thus during this period if right of 'pay is on B street and tramo actuation occurs on A street, right of `way may be held on B street only by closely spaced traillc on B street and if any considerable gap appears in tramo on B street the right of way will be transferred to A street to care for the tramo waiting there. 0n the other hand continous tra'mc on B street can hold the right of way against any waiting tramo on A street until the point O is reached. However if tranic is very light and intermittent and the total supervisory cycle very long it is possible for right of way to be transferred from B street to A street and back to B street during vthe BG-AP period, the right of wayremaining on either street to which it is. transferred for a minimum period before it is retransferred.

Now at the point AP the supervisory cycle begins its preparatory period for A street right of way and if the right of way is on A street at point AP or thereafter'in the AP-O period and O-AG period the transfer of right of way from A street is prevented. If the right of way is on B street however it may remain to the end of the A street preparatory period AP-O. During this period transfer of right of way to A street occurs through normal action of the traffic actuated controller upon any considerable gap in B street tramc'occurring after any A street tralc actuation.

At the point O however and thereafter in the A street right of way guarantee period O-AG transfer of right of way to A street is forced immediately upon A street trafc actuation. As previously described for transfer of right of way to B street during the corresponding B street right of way guarantee period, the transfer of right ofway to A street at point O can be made automatic if desired even in the absence of actuation' on A street.

During the following period AG to BP the tramo actuated controller is free from restriction by the supervisory control and right of way may be held or transferred solely inaccordance with the trafiic demand onthe respective streets as shown by` actuation.

Referring now to Fig. 4 a corresponding supervisory cycle diagram for semi-trame actuated operation as at A street-C street intersection is illustrated. In this case no trafilc detectors are provided on A street and the right of way normally remains on A street in the absence of trafilc actuation of the detectors provided on C street. 'Ihe right of way is transferred by the traffic actuatedcontroller upon actuationon C street and after a period of right of way on C street variable between minimum and maximum 6 umm in accordance with mme schauen on C street, the right of way is transferred back to A street automatically. i

In this case therefore there is no need for any supervisory control periods corresponding to the B street preparatory and B street right of way guarantee periods. 'I'he A street guarantee period is simply extended from the point O through the entire A street right of way portion of the background cycle vto the point T corresponding to the similar point T of the Fig. 3 diagram, and the function -of preventing transfer of right of way from A street is carried through this period.

'I'hus the period from the point T to AP serves as a permissive period for transfer of right of wayto C street if C street traiilc actuation occurs or has previously occurred in the A street portion of the cycle. In trailic actuation has not occurred on C street by the time pointrAP is reached however no transfer of right of way to C street can then occur until the end of the next A street guarantee period. No transfer of right of way to C street is permitted in the A street preparatory period AP to O, but as in the case of corresponding street B in Fig. li tramo on C street can continue tohold right of way on C street until the point O is reached. At the point O the transfer ofi-ight of way to A street is forced immediately (with the usual yellow clearance period) if such transfer has not already occurred. This forced transfer is automatic and occurs in spite of any traffic on C street at that time.

In this semi-actuated operation as well as in the full actuated operation above described however any trame actuating the detector on any street within a short period just before any such forced transfer of right of way from that street is recorded and the effect of such actuation is stored so as to cause subsequent retransfer to that street without the necessity of further actuation there.

'I'he operation of one complete embodiment of the invention in a full traifllc actuated control systemi as illustrated at the intersection of A and B streets will now be described.

Reference is now had to Fig. 5 which is a circuit diagram of one embodiment of the full traillc actuated signal controllerVtogether with its associated traffic signal, trafc detectors, suoervisory control relays and connections to the master controller. It will readily be appreciated that this figure represents merely one embodiment of such a system and that the construction shown is for purposes of illustration only. It is believed that operation of the system will be understood most readily if there is presented first a description of the normal independent operation of a full trafcactuated controller of a type well known in the art and then a description of the supervisory control over such a trafilc actuated controller provided by a master controller in accordance with the invention.

In Fig. 5 RNS, YNS, GNS, REW, YEW, and GEW represent colored signal lamps and lenses of conventional type'for indicating stop. caution and go to the respective A street or north-south and B street or east-west intersecting lanes.

Other typesrof signal indicators as semaphores,

tuatable signal controller for governing'the 0P- acum? eration of the signal lights thru a cycle under the control of the tramo actuatable detectors DNS. DEW. The latter may be switches designed and located to be operated by the pressure of vehicles approaching the intersection, or they may be of a magnetic type in which the approach of the vehicle influences a magnetic V"field to change a circuit, or they may be of hydraulic or other suitable type. Pedestrian operated push buttons or switches may be suitably placed and wired in parallel with the vehicle switches if desired.

'I'he local controller comprises essentially a battery of cams mounted on a common shaft and arranged to close cam contacts CI, C2 etc. in a particular order. The cam shaft is rotated step by step thru its cycle of six positions under the control of a solenoid S which is impulsed at predetermined time periods by either of two condenser-gas discharge tube timing arrangements, one comprising gas discharge tube FJ and co- `operating relay J, the other including tube FK and relay K; and their relation will be explained subsequently. The diagram at the right edge of Figure 2 shows by a black circle or bar which cam contacts are closed in each of the several cam shaft positions.

In the following description of operation of the trafiic actuated controller through one complete cycle of signal indications it will be assumed that both the supervisory relays BS and AS remain cle-energized and that the armatures of the relays complete circuits with their back contacts continuously. This is the normal position of these relays when the master controller is not operating and the individual intersection controllers are operating independently as for example when switch MCS in Fig. 1 is open, or when switches SAS and SBS in Fig. 5 are both open.

vConnection I .-Assume both the switches HNS and HEW to be open, which is the mode of operation ordinarily employed.

Let it further be assumed that the controller isstanding in cam shaft position I, the yellow leaving NS signal position, where a cir-cuit from A. C. positive lead 50 is completed over cam contact C2 I', lamp YNS to grounded lead 5I, thus illuminating the yellow caution signal to the NS street and by a circuit over cam Contact CI I from lead 50 through REW to 5i, the red or stop signal is displayed to the EW street. n

'The length of the period of display of this signal indication is timed by a condenser-gas discharge timing arrangement. From D. C. positive lead 55, over cam contact Cl3, closed in this perlod, a circuit is completed thru adjustable resistance LNS leads 52, 53, condenser QJ to minus lead 5i, thereby charging condenser QJ at a rate dependinglupon the line voltage existing between leads 55 and 5I, the size of condenser QJ and the amount of resistance in theY circuit.

,The direct current for the timing functions of the controller are supplied from the alternating current mains to which the controller is attached by a rectifier VR. or other convenient means. Such a rectifier may be arranged to operate as shown in conjunction with a transformer LXFR to obtain the desired value of direct current potential. l

Considering once more the charging of the condenser QJ, it will be noted that all the factors in the charging of this condenser are constant during the operation of the controller with the exception of the amount of resistance in the periods of the controller, may be predetermined by adjustment of the proper adjusting arm as will appear from the following description.

In parallel with condenser 'QJ there is a.A gas discharge tube FJ, a relay J, lead II, and cam contact C8, which is closed in this position. The tube FJ is of such a character that normally it ls non-conducting, but when the potential across its electrodes attains a certain predetermined value, or threshold conducting EMF, the gas within the tube ionizes and the tube suddenly become conducting. Discharge thru the ionized gas of t e tube is maintained until 'the potential across the electrodes of the tube falls below a second predetermined value, much lower than the first, whereupon the ionization within the tube ceases and the tube again becomes non-conducting. Consequently when the potential across condenser QJ has reached the threshold conducting value of tube FJ, current passes thru the tube and thru relay J in series therewith to operate relay J momentarily. 4

At armature :il relay J completes a circuitv from AC positivelead l0, lead I8, thru solenoid S via armature 1 I to minus lead 5I, operating the solenoid momentarily. The solenoid advances the camshaft from position I to position 2. Also at armature s2 operation of solenoid S completesv a circuit thru low resistance RJI shunting condenser QJ between leads 5l and l2, thus essentially completely emptying condenser QJ of any charge remaining after the discharge ,thru tube FJ. Condenser QJ is now ready for recharging to time the next period from the same initial value, practically nil, from which the preceding period was timed.

In camshaft position 2 cam contact C22 is closed to energize the NS red signal RNS and cam contact C is closed, thus EW green signal GEW is energized. Timing 'in this period `is achieved by the charging of condenser QJ by circuitfrom DC plus lead 55, cam contact CII, adjustable resistance IEW, lead 52, condenser QJ to minus lead 5I. As in position I, when the potential across the condenser (whichis also the potential across the tube FJ, since cam contact C8 is closed) reaches the threshold value for conduction thru tube FJ the latter becomes con...

be called the EW vehicle interval position and its time duration is dependent upon traiiic conditions at the intersection, as contrasted with positions I and 2 which were of predetermined length as set by the preadjusted resistances LNS and g to which the right of way is being accorded, the

condenser QJ is charged up by a circuit from DC positive lead I5 over cam contact CII, adjustable resistance VEW, lead 52 and condenser QJ to minus.

nie vehicle approaching on the NS street actuates one of the detectors DNS which completes the circuit from lead Il thru relay E, lead SI and DNS to lead II energizing relay E. Relay E locks-ln over its amature el, lead 51 cam contact CII, (which is closed in all except position 6) lead Il to minus lead 5I. At armature e2 relay E completes a yield or discharge circuit paralleling condenser QJ thru gas discharge tube FJ,

relay J, lead II, lead 6I, back contact bsl of relay B8, cam contact CII, lead 58, armature e2, to minus lead 5I. Accordingly as soon as condenser QJ charges to the'threshold conducting potential of tube FJ, relay J operates and in turn solenoid S operates to advance the cam shaft to the next position #I to start to transfer right of way to the NS street.

. Should the NS vehicle actuation not take place until after the voltage across condenser QJ has exceeded the threshold conducting potential of tube FJ, the latter will of course not become conducting until the actuation occurs and relay Ev closes the discharge circuit thru the tube as Just traced via armature e2. If no NS actuation occurs this circuit remains open and the cam shaft remains in position 3 with right of way on EW.

l Condition II for right of way on EW.-Vehicle waiting on NS street and light traiiic (i. e. several vehicles) on EWstreet. Condenser QJ comniences to be charged as in the above condition I over resistance VEW. Also as above the vehicle on the NS street actuates detector DNS and locks-in relay E which at armature e2 connects the yield or discharge circuit thru discharge tube FJ, relay J and cam contact CII. Each vehicle on the EW street as it approaches the intersection actuates detector DEW, and each such ace tuation momentarily energizes reIay D. Relay D is not locked-in by these actuations since the lock-in circuit for relay D is open at cam contact C'I in position 3.

During each period of energization of relay D, which will be ordinarily inversely proportional to the speed of the actuating vehicle, armature d2 completes a low resistance discharge circuit paralleling condenser QJ from lleads 53, 52, resistance RJ2 cam contact CI 6;' armature d2, to minus lead 5I, thus reducing the charge on condenser QJ in accordance with the amount of charge on the condenser and the length of time thisyjdischarge circuit is completed. This featui is known as "speed variable reset and the size of resistance RJ2 is arranged so that a vehicle crossing the detector just as tube FJ is vabout to become conducting will cause condenser QJ to be discharged sulciently to give time for the vehicle to cross the intersection while the condenser voltage is again rising to the threshold potential of the tube. Each of the several vehicles, provided they are not spaced too far apart, 'will thus extend the EW right of way period in the manner described and after the last vehicle has crossed the intersection the condenser will have been recharged and tube FJ will operate, energizing relay J and solenoid S in turn in the manner described above to advance the cam shaft to position I.

' Condition III for right of way on EW.-Ve hicle vwaiting on NS street and continuous traffic on EW street.

Under this condition of trafiic at the insection it will be appreciated from the preceding para- 'gra'ph that the continuous trafiic on the EW street will cause condenser QJ repeatedly to be discharged over resistance RJ2. To prevent the possibility oi' such a continuous line of trai'iic from holding right oi.' way indefinitely from vehicles waiting on the other street, a second condenser gas-discharge tube timing circuit is provided to serve as a maximum limit timer.

When relay E is locked-in as described above by the approach of a vehicle on the NS street. a circuit is completed at armature e3 to Vcharge condenser lQK. This circuit extends from D. C. positive lead 55 over resistance MEW back contact and armature asl of relay AS, lead 60, cam contact CI2, leads 6I, 62, condenser QK, lead 61, armature bs2 and its back contact, armature cs2 and its back contact, lead 63, cam contact CII, armature e8 to minus lead 5I. In parallel with condenserQK, between leads 6I and 63, is a circuit including gas discharge tube FK and relay K. The tube FK is arranged to become conducting when the voltage across condenser QK has attained the threshold conducting value of tube FK and the current thru the tube will operate relay K. The period of the K timing circuit is arranged to be considerably greater than the period of the J timing circuit in the vehicle interval positions. It will be noted that cam contact 4I enables this maximum timing circuit to be active continuously thru positions 2 and 3 beginning with the arrival of a vehicle on NS causing closure of contact e3. Relay K at armature kI completes the energization circuit for solenoid S from A. C. plus lead 50, lead 56, solenoid S, armaturekI, to minus lead I.

Further, operation of relay K causes the detector relay associated with the street from which right of way is being transferred to be energized and locked-in. At armature k2 a circuit from minus lead 5I is connected over dual contacts to energize both detector relays D and E. Relay E however has already been energized by DNS actuation and has been locked-in over its contact eI so that the circuit over contact k2 for energizing relay E at this point now has no signicance. Upon energization by contact k2 relay D is locked-in by a circuit from A. C. plus lead 50, relay D, armature dI, lead 65, armature s3 (while solenoid S is energized), back contact :i2 (assumed closed), cam contact C I 8, lead 58 to minus lead 5I, and after solenoid S is de-energized and has advanced the cam shaft into position 4 this lock-in circuit is completed over lead 65, cam contact C'I, lead 58 to minus lead 5|. It will be understood that solenoid S is arranged to so shift the cam shaft only during its movement returning to normal from its energized position. Thus when the right of way is forcibly removed from a street by the maximum timer, armature k2 cooperates with armature s3 and serves to lock-in the detector relay of the street from which right of way is being removed in order that vehicles stopped by such a transfer without suicient time to clear the intersection after actuating the detector may be permitted to proceed by the recall of right of way to that street at the earliest opportunity consistent with trafc on the other street but at the longest within the maximum period for the other street.

If both condensers QJ and QK should reach the conducting potentials oi.' their respective discharge tubes FJ and FK simultaneously, both relays J and K would be operated, and since under these conditions relay J has been operated indicating that .suicient time has elapsed for the last actuating vehicle on the EW street to cross the intersection, relay D should not be locked-in since no vehicle will have been forced to stop. Accordingly although relay K operates amature k2, the locking-in circuit over armatures-12 and s3 is not completed since relay J operates and opens the circuit at amature 12', and consequently relay D will not be locked-in under this condition.

Relay K, when operated, at armature k3 completes the circuit thru tube FJ and relay J shunting condenser QJ, but this has no significance here since a corresponding circuit has already been completed via contact e2 and cam CI1 and the purpose of this circuit will be subsequently explained.

On any shift of the cam shaft from positions 3 or 6 the solenoid S completes at armature sI a discharge circuit for condenser QK over leads 62, 6I, cam contact C3I, amature sl, resistance RKI, lead 61, condenser QK. Thus condenser QK will be prepared to commence its next timing interval from a discharged condition. At armature s2 condenser QJ is similarly discharged in the manner aforedescribed.

In position d of Vthe cam shaft cam contacts C22 and CI@ are operative to energize the NS red Isignal RNS and the EW yellow, YEW. Condenser QJ is charged by a circuit from D. C. positive lead 55 cam contacts C2, adjustable resistance LEW, leads 52 and 53, and when the potential of the condenser has reached the threshold conducting potential of tube FJ, the tube becomes conducting, operating relay J and in turn solenoid S to advance the cam shaft in the manner previously described to position 5, the NS initial position. Cam contacts C9 and CII are now closed energizing respectively the NS green signal GNS and the EW red signal REW. A charging circuit for condenser QJ is completed over adjustable resistance INS and cam contact C3 to charge condenser QJ to the threshold conducting potential of tube FJ which operates in the aforedescribed manner and the cam shaft advances to the NS vehicle interval position 6. l

In position 6 the signal indications remain as they were in position 5. The duration of this period is also dependent upon traiiic conditions at the intersection and the operation of the controller is similar to the operation described for Vposition 3 excepting that now right of way is on the NS street instead o! the EW street and' the eects of trame actuation on the two streets are now interchanged. It is believed that with the summary presented below concerning operation under three conditions of traffic such operation will bereadily understood in view of the complete description presented in connection with position 3.

Condition I for right of way on NS.-No tralc on NS street and vehicle approaches on EW street.

The vehicle approaching on the EW street actuates detector DEW and relay D which is lockedin over armature dI, cam contact C'I and lead 58 to minus lead 5I. At armature d2 relay D completes the yield or discharge circuit for condenser QJ thru gas discharge tube FJ, relay J, lead 54, lead 66, back contact and armature asI of relay AS cam contact C6, contact d2 to minus lead 5I. As soon as the potential on condenser QJ reaches the threshold conducting voltage of tube FJ relay J operates to advance the cam shaft to position I.

Condition II ,for right of way on NS.-Vehicle waiting on EW street, light traffic (i. e. several vehicles) on NSstreet.

Inthis condition condenser QJ, which is being charged meanwhile over adjustable resistance VNS and cam contact C4, is reset by vehicles approaching on the NS street to hold right of way from being transferred to street EW. Each actuation of detector DNS and consequent energization of relay E, at armature e2 completes a low resistance discharge circuit for condenser QJ from leads 63, 62, resistance RJ3, cam contact C6, lead 6l, armature e2, to minus lead 6I. The charge on condenser QJ will an appropriate time after the last NS vehicle has actuated detector DNS reach the critical potential of tube FI and operate relay J to cause shift on the cam shaft form position 6.

Condition III for right of way on NS.-Vehicle waiting on EW street, continuous trafllc on NS street.

As in Condition II, the charge on condenser QJ which is being increased by the charging thru resistance VNS is subjected to resetting by vehicles actuating detector DNS in the sereet having right of way. If the trafnc flow is substantially continuous the voltage across condenser QJ will not reach the critical potential of tube FJ due to the continued resetting. via resistance RJ3. The maximum timing circuit, which becomes operative upon actuation on the opposing street, street EW, is effective meanwhile, and condenser QK is charged by circuit from lead 55 over resistance MNS, back contact vand armature bs4 of relay BS, cam contact CI, leads 6I and 62, lead 61, back contact bs2 of relay BS, back contact cs2 of relay AS, cam contact C30, contact d3 of relay D to minus lead 5I. When the voltage on condenser QK reaches the critical potential of tube FK, the latter becomes conducting and relay K is operated. In turn over armature-Ici solenoid S is operated to advance the cam shaft to position I and thus initiate transfer of right of way from the NS to the EW street.

A complete lcycle of operation has now been described. It will be seen when the local controller is operating independently, that is, when both supervisory relays AS and BS are de-energized that right of Way will remain on one street -in the absence of trailic actuation on the other street; that right of way will, after the expiration of a minimum or initial period, be transferred immediately to the other street in response to trailic actuation on the latter street, but trailic on the street possessing right of way may postpone such transfer up to a predetermined maximum time.

Connection `II.-Arteria1 on recall switch HNS closed and switch HEW open.

With recall switch HNS closed, it will be seen that in 9.11 camshaft positions except Ns vehicle interval position 6 a circuit will be completed from plus lead 50 thru relay E, lead 64, lead 68, switch HNS, lead 51, cam contact CI8 and lead 58 to minus lead 5I. 'I'hus relay E Will be energized in all except position 6. The effect of such operation will be to place an artificial call or traffic actuation on the NS street whenever right of 4way is not accorded thereto so that right of way will be returned thereto automatically after any gap in EW traflic during position 3 suiiic1ent to permit the condenser to charge up and operate the tube FJ, or after the EW maximum interval` if no a pears in the EW trafllc.

Sinewth3 circuit thru switch HNS is open at cam contact CIB in the NS vehicle interval position 6 the relay E is energized in this position only upon actuation of one of the detectors DNS,

and theswitch HNS thus has no holding effect on NS right of way.

Thus with connection II right of way reverts automatically to NS or A street and in the absence of traiilc on EW or B street right of way remains onfA street. l

' Connection III .-Arterial or recall switch HEW closed and switch HNS open.

Withrecall switch HEW closed, a circuit is completed via cam contact C'I to energize relay D in all positions except #3 the EW vehicle interv val position. Thus this switch serves to cause automatic recall of right of way to EW in the same fashion as switch HNS causes recall of right of way to NS as described above under Connection II.

With Connection III right of way reverts automatically to B street and remains there normally in the absence of tranic on A street.

Connection I V.;Both recall switches NHS and HEW closed. l

With both switches HNS and HEW closed relay vD is energized in all positions except #3 and relay E is energized in all positions except #6 so that the right of way is recalled automatically to each street from the other and in the absence of trame on both streets the right of way reverts back and forth at minimum intervals including one initial interval, one vehicle interval, and one yellow interval on each street. Traiilc on NS during the NS right of Way period is able to prolong the lright of way period up to the NS maximum, and trailic on EW during the EW right of way period is able to prolong the right of way period up to the EW maximum.

Having now described the operation of the full traiilc actuated local controller as independent of supervisory control, the operation of the same under the control of the supervisory relays and master controller in accordance with the invention will now be described.

At the upper left side of Fig. 5 the portion of the master controller of Fig. 1 associated with the intersection of A street and B street is repeated to aid in tracing the operation of the supervisory control on the local controller of Fig. 5. It will be appreciated that the cyclic contact devices MBI and MBZ may be either located at a central point and operated cyclically by the m0- tor M in common with the corresponding contact devices for the other intersections as shown in Fig. 1, or these devices may be located at the respective intersections and driven by separate motors, employing motors of the synchronous type or synchronized with each other by any of the well known methods at each intersection.

The master controller contacts MBI and MB2 are connected to supervisory relays AS and BS respectively, the latter relays being shown on the lower left side of Fig. 5. The switches SAS and SBS are provided to permit either or both of these relays to be disconnected and may be operated locally or. by remote control by means of an auxiliary electromagnet not shownY for example in accordance with well known practice.

The supervisory relayseach have a number of contacts connected to the local controller to provide control of the transfer of right of way bythe latter, particularly from camshaft positions 3 and 6 the vehicle interval green signal positions for the respective streets B and A.

The contact devices MBI and MB2 are arlranged in proper time phase relation with the corresponding master control contacts for the ous transfer of right of way at all intersections or for progressive transfer for progressive tramo movement along A street for example. In Fig. l and in the related showings of the master conl trol contact devices in Figs. 5, 6, and 7 the contact closure periods are shown in spaced phase relation as they might be arranged for progressive movement along A- street for example, it being assumed for ease of comparison between the full actuated 'and semi-actuated operations illustrated at A street-B street intersection and A street-C street intersection respectively that the preferred transfer points in the background cycle are in phase, with A street portion-,pf the background cycle about 65% of the total and the B street and C street portions of the cycle about 35%. It will be understood that these figures are used for illustration only and that the contact periods lcan be arranged for any proportion of the cycle and any phase relation desired. The 35%-65% division of the background or supervisory cycle thus assumed for Fig. and Fig. 6

' conforms approximately with the corresponding cycle diagrams in Fig. 3 and Fig. 4.

Considering now Fig. 5 in relation to Fig. 3 the top of the contact discs MBI and MBZ in the position shown in Fig. 5 corresponds with point O on the cycle diagram of Fig. 3 as the preferred point for transfer of right of way to N-S or A street, and the portion of these discs approximatelyI 240 degrees of arc clockwise around the circle corresponds with point T on the cycle diagram.

It will be seen that the unshaded or conducting portion of the contact disc MBI extends some distance on either side of the top and this corresponds with the A street preparatory period of Fig. 3 to the left of the top and extending thru the A street right of way guarantee period to the right of the top. Thus assuming switches MCS, SAS and SBS closed, as is the case for supervisory control operation, as the two discs MBI and MBZ rotate in-phase the relay AS is rst energized by contact MBI V for a portion of the master control cycle and then de-energized, and later relay BS is energized for another portion of the cycle and de-energized, these portions of the cycle corresponding with portions AP to AG and BP to BG respectively of the cycle diagram of Fig. 3.

The actual effects of -such periodic energization of relays AS and BS on the transfer of right of way depend on which position of the cam shaft the local traillc actuated controller is in and the presence or absence of trame on the streets as recorded by actuation of the detectors DNS and DEW.

If either relay AS or BS is energized during one of the yellow signal periods with the local controller on position I or position 4 for example, the local controller proceeds with normal timing of this period and shifts to the next position ywithout interference from the supervisory control.

Also in the initial interval positions 2 and l of the local controller the energization of either relay AS or BS does not restrict the normal time of these intervals. and although the proper preparatory interval timing is initiated by these relays in this position as will be subsequently described, the controller shifts from either initial interval position to the next without restriction.

`In the vehicle interval positions however the corresponding to the'supervisory control functions described in connection with Fig. 3. If relay AS is energized while the local controller is on the NS vehicle interval position 5 with right of way on A street for example, the local controller-is prevented from shifting from this position and thus the transfer of right of way from A street is prevented. If relay AS is energized while the local controller is in the EW vehicle interval position 3 with right of way on EW, the shift of the camshaft from position 3 can occur in the normal manner by the operation of relay J through tube FJ by condenser QJ as aforedescribed under Condition I or "Condition II for "Connection I during the first part of the energization period of relay AS. During this part of that period however the normal timing action of the condenser QK as a maximum timer is interrupted by relay AS, and condenser QK- and its associated tube FK and relay-K are employed to time a period corresponding substantially with the A street preparatory period of Fig. 3, at the end of which period and thereafter until relay AS is again de-energized the shift of the cam shaft from position 3 is caused immediately upon energization of relay E by actuation of the detector DNS if such shift has not already occurred normally by operation of the J relay as above. 'I'his action causes a forced transfer of right of way from B street. The circuits for causing this action will be subsequently described.

vSimilarly if relay BS is energized in the EW vehicle interval position I vwith right of way on B street the shift of the cam shaft from this position will be prevented, and if this relay is energized in the NS vehicle interval position 6 of the cam shaft, after a preparatory period timed by condenser QK the shift of the cam shaft from this position is forced immediately upon energization of relay D. The time periods of condenser QK upon energization. of relays AS and BS are preferably adjusted to be a few seeonds shorter than the actual preparatory period of the background cycle as determined by the setting of the MBI and MIBZ contact periods in order to allow for the yellow signal intervals. For instance if the yellow interval following B street green is 3 seconds and the A street preparatory period of the background cycle is 18 seconds the adjusting resistance APNS is preferably set to give a 15 second period for charging condenser QK during the first part of the time relay AS is energized.Y

The circuits for the several functions of the AS and BS relays as aforedescribed will now be traced. First assuming relay AS to be energized andthe local controller to be in cam shaft position 6 the NS vehicle interval position, it will be seen that right of way is on A street. In this position by reference to the operation in Condition I and Condition II for right of way on NS under Connection I aforedescribed it will be observedthat the circuit for operation of tube FJ and relay J by condenser QJ through closure of contact d2 of relay D includes the back contact asi and thus the opening of the contact asl by energization of relay AS opens this circuit and thus prevents energization of relay J. Also at contact asi which is now closed, a circuit is completed to maintain the condenser QK discharged and thus prevent the operation of tube FK and relay K. This circuit may be traced from the right side of QK via lead 62, lead 6I, camcontact CI, lead contact as5, low resistance HKS, lead 61 to the left side of QK. A

Since both relays J and K are thus prevented from operating, the energizationof solenoid -S and the consequent transfer of right of way from A street is prevented, while relay AS is energized.

tion and in the completely deenerglzed position of relay AS but is closed momentarily upon initial energization or initial de-energization of the relay.

Also when relay AS is energized a circuit is completed for charging condenser QK to time the auxiliary interval corresponding to the A street preparatory interval if the right of way is on B street, i. e. if the -local controller is in position 2 or 3. This circuit extends from D; C. positive lead 55, time adjusting resistance APNS, lead 10, contact asl, lead 60, cam CI2, lead 6|, lead 62, QK, lead 61, back contact bs2, front contact as! to minus lead 5|.

Condenser QK will thus charge up and after an interval dependent upon the setting of adjusting resistance APNS the voltage acrossthe condenser will reach the threshold conducting yvalue of tube FK. The end of this time'period corresponds substantially with point O on the cycle diagram of Fig. 3, with allowance vfor the YEW. clearance interval.`

'Ihe circuit operation of relay K through tube FK from the charge on condenser QK will not be completed however unless or until the relay E is energized to close contact e3, assuming that switch TNS, the function of which will later be described, is open. This circuit' via relay K is closed when e3 is closed and extends from the right side of QK,`lead 62, lead 5I, tube FK, relay K, lead 63, cam CM, contact e3. to minus lead 5|, which is connected via make contact as2,- back contact bs2, lead 61 to the left side of QK.

'I'hus as soon as relay E is energized by traffic on A street the condenser QK will discharge thru tube FK and relay K and cause shift of the cam shaft from position 3 resulting in transfer of right of way,after the yellow interval, to A street. It will be noted that, as in the case of this condenser QK serving as a maximum timer in the normal fashion, the operation of relay K causes the shift from position 3 irrespective of traffic on B street and therefore causes at contact k2 energization and lock-in .of relay D, if relay J is not operated simultaneously, so as to cause right of Way to return later to B street to care for trafficthus interrupted by transfer of right of way from B street.

Thus with switch TNS open the relay AS in cooperation with the condenser QK and charging resistance APNS serves to force upon A street actuation the immediate the transfer of right of way toA street at the point O and thereafter during the A street right of way guarantee period of the supervisory cycle.

If it is desired to cause transfer of right of way to A street at point O (if transfer has not already occurred) even in the absence of trai'- fic actuation on lA street in order-to carefor pedestrians, or .to prepare for the expected progressive wave of vehicles, or other reason, the switch TNS is closed and the circuit for operation of relay K by the discharge of condenser QK through tube uFK is thereby completed via TNS and make contact asB to negative lead 5l thus shunting the contact e3 on relay E and causing operation of the solenoid by relay K even in the absence of actuation of DNS.

Under this condition contact k3 completes the operating circuit for relay J from condenser QJ so that if yrelay J has been charged to the threshold potential of tube FJ thus indicating that suiilcient time has elapsed after the last actuation for all EW vehicles to clear the intersection, relay J Will be operated and at its contact :i2 will prevent the locking-in of relay D and' consequently prevent unnecessary recall of right of way to the EW street. If condenser QJ is not so charged suiiciently, however. tube FJ will not be rendered conducting and clossure of contact k3 will not energize relay J. Consequently relay D will be locked-in as contact il.` will remain closed. The time and order of operation of the contacts on relays J and K are arranged so that contact' 7'2 remains open until after k2 has opened on de-energization of relay K if both ofA theserelays are operated simultaneously.

Considering now the effects of operation of supervisory relay BS it is noted that this relay is energized during the yclosed contact period of master control contact MBZ, which corresponds with the period BP to BG in the supervisory cycle diagram of Fig. 3.- It will be seen that contact MBI is thus open and relay AS de-energized at that time.

Relay BS has the same functions' with respect to preventing transfer from and forcing transfer to B street as relay AS has for A street as described above. The transfer of right of Way from B street is prevented .by the opening at back contact bsl of the relay J operating circuit via contact e2 of the relay E, so that the solenoid S will not be operated by contact :il in the EW vehicle interval positionA 3. Also kat front contact bs5 the condenser QK is kept discharged in position 3 by a circuit from the right side of QK via lead 62, lead 6I, cam contact CI2, contact bs5, low resistance RK5, lead 61, to the left side of QK. This prevents QK from'being charged and thus relay K cannot be energized to operate solenoid S. Consequently solenoid S cannot be operated in position 3 with the BS relay energized and right of way is held on B street.

If the cam shaft is in position 5 or 6 when relay BS is energized a charging circuit for condenser QK is completed via adjusting resistance BPEW and make contact bsl to time a prepara- A tory interval for B street corresponding substanbs3, This momentary discharge prepares the condenser QK for timing the B street preparatory interval. This circuit is also completed momentarily on de-energization of relay BS to discharge QK so that the forced transfereect will not carry into the BG-AP period.

After the preparatory interval for B street, timed by condenserA QK in co-operation with resistance BPEW and contact bsl. condenser QK is charged tothe threshold voltage of tube FK and for aperiod corresponding to the T-BG portion ofthe of the local controller from position 6 is caused immediately by operation of tube FK and relay K and consequently solenoid S. if or as soon as relay D is energized closing contact d3 (assuming switch'TEW open), thus forcing the transfer of rightof' way to B street if any traiiic is on B street. y

This circuit for operating relay K extends from QK via lead, lead tl, tube FK, relay K.'lead 63, cam" contact C30, contact d3, negative lead Il, which via contact bs2, lead 61 is connected to the other side of condenser QK. If there is no traffic on B street relay D will remain de-en ergized and relay K will not be operated to shift from position will not occur and right of way will remain on A street.

It will be appreciated` that during the preparatory interval for B street the shift from position 8 can occur in normal fashion as aforedescribed under Condition I and Condition II for right of way on A street by operation of the relay J if relay D is operated by tramo on B street and therey is no trafiic actuation on A street for a sufcient time to permit condenser QJ to charge to the threshold-voltage of tube FJ. ,Y Switch TEW, which was assumed open in the above description, can be closed if desired to cause automatic shift from position l at point T even if relay D remains de-energized as in the absence of traffic on B street. This is accomplished by a circuit shunting contact d3 via make contact bsB and switch TEW to negative lead 5I.

In any case of operation of relay K to cause a forced shift from position 6 the relay E is energized over contact k2 in case relay J is not energized at that time so as to recall right of way to A street for the protection of trafilc that may be interrupted as aforedescribed in the case of corresponding interruption of tranic on B street by forced shift from position l.' n

It will be noted by reference to the contact discs MBI and MBZ that supervisory relay AS is energized only during the preparatory period for A street and the guarantee period for A street, and that supervisory relay BS is energized only during the preparatory and guarantee periods for B street, both relays being de-energized for the two intervening periods. During these intervening periods corresponding with period AG to BP and period BG to AP in the cycle diagram of Fig. 3 therefore the local controller is free from supervisory control and the operation Vof the local controlled is independent as nrst described with both relays AS and BS de-energized. the transfer of right of way after the normal minimum periods then bcing dependent solely on traffic actuation.

'Ihus it will be seen that by means oi' the supervisory relays in co-operation with master cycle diagram of Fig. 3, the shift its preferred portion of the master control supervisory cycle and then to the other street in its preferred portion of the cycle.

At the beginning of the preferred right of'way portion of the cycle for one street right of way transfer to that street is preferably forced immediately inA event of actuation on that street if right of way has not already been trans- .ferred to that street. At that time and for a short period before the end of the preferred right of way portion of the cycle for the other street the transfer of right of way from said one street to said other street is prevented il the right of way is already accorded to said one street. In intervening portions of the cycle with right of' way on either street the transfer of right of'way is governed preferably by tralc actuation independently of the supervisory control. f

Now referring to Fig. 6 in connection with Fig. 4 the operationV of the one form of supervisory control over a semi-.trame actuated local controller will be described.

It will be recalled that in the description of Fig. 4 it was pointed out that tramo detectors are located only in theV C street or EW and the right of way remains normally on the A street or NS in the absence of actuation on C street, the right of way being transferred to C street in the event of actuation there and after a period variable by further actuation between a minimum and a maximum the right of way is retransferred automatically to A street.

This form of operation is accomplished simply by closing switch HNS and properly adjusting the initial interval and vehicle interval resistances INS and VNS to provide a proper protective minimum period for A-street traffic.

control contacts MBI and-MB! the transfer of right of way by the local trame actuated controller. is cyclically controlled so as to favor the according of right of way first to one street in In Fig. 6 the local controller is shown of the same construction as that of Fig. 5 except that with the omission of supervisory relay BS which is not required in semi-actuated operation the circuits ordinarily passing through the back contacts of relay BS now are completed directly in Fig. 6 with the same effect as having these back contacts of relay BS permanently closed in Fig. 5. In addition the B- street preparatory timing interval is not needed and the adjusting resistance BPEW of Fig. 5 for this interval is omitted in Fig. 6. Also the switch TNS and associated contact asl of relay AS of Fig. 5 is not needed in semi-actuated operation as relay E is always energized in position I of the cam shaft where switch TNS would only be effective if relay E were de-energized.

With these minor changes the ,circuits and fundamentals of operation of the local controller in Fig. 6 are the same as already described for full actuated operation and need not be re peated, it being noted however that in the senilactuated type of operation as in Fig. 6 the relay E remains energized in all positions except the NS or A ystreet vehicle interval position l as described in Connection II, and to aid in visualizing the semi-actuated operation this relay E is shown energized in Fig. 8 as in any of positions I thru l inclusive.

If relay AS is assumed to be de-energized continuously as in the case of switch SAS beins in theopen position, the local controller is independent of any supervisory control and acts as an individual semi-traffic actuated controller.

There are a few main differences to be noted in the semi-actuated operation from the full ing relay K as previously described, the superactuated operation. The maximum timing ac-` tion via MNS resistance for limiting A street right of way is not needed and is therefore normally set longer than the desired A street right of way period, and the latter is `determined by the total of the initial interval plus the vehicle interval for A` street as determined by the udjusting resistance INS and VNS. 'I'he relay E being de-energized in position 6 the condenser QJ continues to be charged without discharging action up to at which point the relay J operates to initiate transfer of right of way toV B4 street on any B street trame actuation of DEW and consequent energization of relay D, assumingy that relay AS is de-energized and contact asl closed. I f D is not operated .the condenser continues to charge above the threshold value to line voltage and the local controller rests on position 8 with right of way on A street.

In addition it will be appreciated that in independent senil-actuated operation the timing of the maximum period for the cross street C or EW right of way is started with the charging oi condenser QK at the beginning of the EW initial interval in position 2 when cam contact CI 2 closes since contact e3 of relay E is closed in this position. It will be further noted that with relay E always energized in the EW vehicle interva position 3 the condenser QJ operates relay J via tube FJ and causes the solenoid S to initia'te transfer of right of way from C street as soon as there is 4a sum-cient gap in EW or C street. traiiic to permit the condenser QJ-to reach the threshold voltage of tube FJ.

With the above briefly described differences in mind the supervisory control operation will now be described for Fig. 6 in connection with the corresponding supervisory cycle diagram in Fig. 4.

Only one master control contact device MCI is now required and this is arranged to close and maintain relay AS operated for a period corresponding with the AP to T (clockwise) portion of the supervisory cycle diagram of Fig. 4, This entire period serves as a preventive period for transfer of right of way from A street, the

the threshold voltage of tube FJ,

remainder of the cycle from T to AP serves as I a permissive period for transfer of right of way to C street if traiilc actuation on C street occurs or has previously occurred since the last previous right'of way period for C street.

This preventing of transfer of right of way from A street occurs through energization of relay AS and consequent interruption of the relay J operating circuit in position 6 of the cam shaft just as afore-described for fullv actuated operation. v

Correspondingly the energization of relay AS serves in cooperation with adjusting resistance APNS to employ the condenser QK, to time the A street preparatory interval by charging condenser QK over a circuit from D. C. positive lead 55, resistance APNS, lead 10, contact asl, lead 60, cam contact CIZ, leads 6I, 62, condenser QK,

lead 6 1, make contact as2 to minus lead. 5I, which corresponds to a similar circuit previously described for full actuated operation.' lIf right of Way is on C street during this interval it is transferred to A street upon any gap in C street traflic `suiiicient to permit condenser QJ to be charged to operate relay J If there is no gap in C street traflic however the transfer of right of way to A street is forced at point O of the cycle diagram thru action of condenser QK in operatvisory control thus serving as an automatic maximum limit to right of way on C street.

During the C street permissive period, i. e. when relay AS is de-energized, transfer of right of way from A street occurs on any C street traillc actuation previously recorded or if there is none such then at the first C street actuation occurring during the permissive period. f

'I'he local controller could of course be arranged to provide only a predetermined time period of right of way to C street not subject to variation by actuation simply by omitting RJ2 and having an open circuit at this point, but preferably it is arranged as shown.

An alternative form of supervisory control employing essentially the same fundamental prin- `ciples and using the same type of full actuated controller as in Fig. 5 is shown in Fig. 7. In this case :however in lieu of using only the master control contact devices MBI and MBZ and employing the .condenser QK timing circuit to time the preparatory intervals in cooperation with relays AS and BS, these periods are cared for by providing two additional contact devices M83 and MBl to operate added supervisory' relays AST and BST respectively.

I'he relays AS and BS of Fig. 7 are arranged to be energized throughout the periods AP to AG and BP to BG respectively in the supervisory cycle of Fig. 3 as in Fig. 5, and these relays retain theirfunction of preventing transfer from the respective streets A and B as before described. Contacts asl and bal when open prevent the operation of relay J in position 6 and position 3 respectively, and the contacts asi and bs5 when closed prevent charging of condenser QK and consequently prevent operation of relay K in these respective positions, all as aforedescribed in connection with Fig. 5. The armatures as2, as3, and asl are omitted as well as corresponding armatures bs2, bs3, and bsd as unnecessary in Fig. 7 and the circuits passing through the back con'- tacts associated with these armatures are permanently completed directly.

The function of forcing transfer of right of way in the proper portions of the background cycle is performed by supervisory relays AST and BST of Fig. 5 in co-operation with master control contacts MB3 and` MBL 'I'he latter are arranged to energize relays AST and BST throughout the O to AG and T w BG portions of the supervisory cycle, respectively corresponding to the right of way guarantee periods.

The relay AST, energized at point O serves to force the transfer of right of way to A street on any trailc actuation on that street if such transfer has not already occurred, and if no such actuation has occurred at that-point it maintains the local controller in readiness to transfer right of way immediately to A street upon the first actuation there during the A street right of way guarantee period, assuming that switch 'I'NS is open as shown. This function is accomplished thru the closing of make contact ast3 which places a shunt thru relatively low resistance RKG across the normal EW maximum time adjusting resistance MEW so as to charge substantiallyimmediately condenser QK to or above the threshold voltage of tube FK regardless of what the normal time setting for the EW maximum period is.

Although this shunting circuit across resistance MEW is effective to charge the `condenser QK quickly in positions 2 and 3 of the cam shaft through cam -CI2 this does not reduce the period in the initial interval position to a very small value since the relation of the 'time of operation of relays AST `and AS and the timing of the initial interval is such that thru the action of relay AS in preventing transfer of right of way from A street, afterk point AP the local controller if giving right of way to B street just before point O must have already passed thru the initial interval.

This rapid charging of condenser QK by relay AST via contact ast! prepares the condenser QK for its immediate operation of relay K upon closure of the relay K operating circuit at contact e3 of relay E as already described for Fig. 5 and thus cause shift from position 3 and transfer of right of way from B street. If or as soon as traillc actuation occurs on A street and relay E is energized the transfer of right of way to A street is forced immediately if such transfer has not already occurred.

If the right of way is still on B street at point AG of the cycle on account of absence of actuation on A street, the de-energization of relay AST at this point will at its momentary makebreak contact ast2 discharge condenser QK over low resistance RK2 so A street actuations during the AG-BP period will not force transfer to f A street, assuming proper adjustment of contacts ast and ast3.

As aforementioned this action assumes that switch TNS is open. If it is desired to have automatic transfer at point 0 in the supervisory cycle the switch TNS is closed and the relay AST then over make contact' asti and switch TNS shunts the contact e3 and completes the operating circuit for the relay K from the condenser QK irrespective of the condition of relay E.

The relay BST, energized at point T in the supervisory cycle, serves to force transfer of right of way to B street on B street actuation if such transfer has not already occurred. This is accomplished by shunting the normal maximum timing` resistance MNS with relatively low resistance RKC via make contact bst3, thus causing quick charging of condenser QK in the NS vehicle interval position 6 over cam CI in the same fashion as previously described for relay AST in position 3.

With condenser QK charged the shift from posinon s is caused (assuming switch TEW open) as soon as relay D is operated to close through contact d3 the operating circuit of relay K. If no traffic actuation on B street has yet occurred the' condenser QK remains charged and the shift from position 6 occurs immediately upon.

the first actuation to occur on B street during the B street right of way guarantee period.

At the moment of de-energization of relay BST at point BG the condenser QK is discharged over contact bei! and low resistance RKI, so as to discontinue the forced transfer eect.

If it is desired to have automatic transfer of right of way to B street at point T irrespective of trame actuation, the switch TEW is closed, and then energization of relay BST will at make contact bstl and via switch 'I'EW shunt contact d3 'of relay D, thus rendering the circuit for operating relay K from condenser QK independent of thecondition of relay D.

It will be understood that the contact periods of relays AST and BST could if desired 'by properly arranging the segments of contact discs MBS and MBl be made to extend beyond the point AG and BG respectively even though relays AS paratus and BS are de-energized at these points. The effect would then be that transfer of right of waylto A street for example would be forced by any A street actuation occurring while right of way is on B street even though the right of way holding effect on A street by relay AS had ceased. Thiseifect could be continued untiljust before point BP in the ly similar forced transfer to B might be provided for from point T until just before point AT.

It will also be readily appreciated that the apof Fig. '7 could be arranged for semiactuated operation by closure of switch HNS by properly setting the time adjusting resistances as previously outlined in connection with Fig. 6. The relays BS and BST could be retained deenergized by opening of switches SBS and SB'l' for semi-actuated operation, or as in Fig. 6 these relays could be omitted and the circuits now shown through their back contacts permanently completed as if the contacts were always closed. In the latter case only master Vcontrol contacts MBI and M133 would be required.

It will be further appreciated that the apparatus of Fig. 6, with the EW detectors DEW omitted, the switch HEW closed as well as switch HNS, and the adjusting resistances IEW and VEW properly set to provide a surn of the initial' and vehicle intervals of slightly greater than the EW (or C street or Z street) portion of the supervisory cycle, the local controller will serve as a fixed time or non-trame actuated control system and as a part of the entire co-ordinated system, as indicated at the intersection of A and Z streets in Fig. l. In this case the automatic transfer of right of way to A street will always occur at point O of the supervisory cycle, in spite of the uncompletion of the QJ condenser time period, thru action of relay AS, and the right of way will always be transferred at point T of the supervisory cycle to Z street, at de-energization of relay AS, since relay D will be energized at this time thru switch HEW. Thus for fixed time operation only one master control contact and one supervisory relay is required.

It will thus be seen that in accordance with the invention a very flexible type of co-ordinated traffic control system is provided by means of which individual traffic actuated signal systems at one or more intersections can be supervised in relation to each other or in relation to nontraillc actuated systems to favor trailic movement through the group of intersections in accordance with a predetermined progressive or other plan, and yet provide for variation from that plan to better serve trailic at the individual intersections when such trame varies from the predetermined plan, such variation from the plan being arranged to have a minimum of interference with trame moving thru the several intersections in accordance with such plan.

It will be apl.L :ted by those skilled in the art that although contacts MBI, MBI, etc. are shown closed to energize relays AS and BS respectively during the periods AP to AG and BP to BG respectively, the conducting and non-conducting segments could be interchanged and the relays AS and BS `could have their make contacts generally interchanged with their break contacts except in the case of contacts asB and bs3 so that these relays would perform their preventive function etc. when de-energized instead of when energized as shown. These relays and master control contacts are preferably arranged as shown however so that in the event of failure cycle if desired. Corresponding- 

